This invention relates to addressing of disk drives and, in particular to a disk drive, method and memory media that have a capability of addressing two or more sizes of blocks of data on the disk.
In the past, disk technology has advanced at a rate that allowed increased density with little degradation of the read process, so that reliability of retrieving data has been relatively constant. Where degradation occurred, the solution was to use powerful error-correcting codes. Any redundancy associated with these codes was minor when compared to the disk capacity compound growth rate of about 60% per year.
It is expected in the future that recording density increases will stretch the limits of the technology. As this happens, reliable reading will depend strongly on enhanced error correcting codes that will require significantly more information in a data block to assure proper performance of the read process. Moreover, the overhead needed for clocking data, decoding data and correcting errors will be substantial. As most of this overhead is per block, rather than per byte, processing of short blocks will be much less efficient than that for longer blocks. The result is that users will not realize the full benefit of increased density in the future.
To address this situation, the National Storage Industry Consortium has proposed to increase the physical block size on a disk from a de facto standard of 512 bytes to 4,096 bytes. In the not too distant future, as recording densities reach 100 Gbits/in2 with degraded raw error rates, the change to a 4,096-byte block size is expected to increase the disk capacity, as seen by a user, by 25% to 30%.
Any changeover to the 4,096-byte block size must consider the legacy software that is based on a 512-byte block size.
What is needed is a solution that allows legacy software based on 512 byte block size to continue to work with no change, while allowing new software based on a 4,096 byte block size to also work on the same disk drive.
The present invention provides such a solution with a change that allows both legacy software and new software to work concurrently in the same disk drive control system. The method of the invention stores a mode page that contains a first field signifying a native block size N. A command provided from a host computer is also stored. The command includes a command block size S, a command block address B and a command transfer length L. If the native block size N and the command block size S are equal, the command is executed using the command address B and the command transfer length L for accessing data. If the native block size and the command block size are unequal, the command block address and the command transfer length are converted to a conversion address and a conversion transfer length. The command is then executed using the conversion address and conversion length for data accesses. By allowing the command to carry the block size information, both legacy software using a data block size of 512 bytes as well as new software using a data block size of 4,096 bytes can both use the same disk drive with only a modest change that can be implemented in hardware, firmware or software.
The disk drive of the invention includes the hardware, firmware or software that implements the method of the invention. The memory media of the invention includes the software that controls the disk drive to perform the method of the invention.